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Darwin Correspondence Project

From William Erasmus Darwin   5 July [1869]1


July 5

My dear Father,

I went to Alum Bay Hotel yesterday, and walked to Colwell Bay where after some little search I found a considerable number of Epipactis P. tho’ with not v. many flowers out.2 I send you in little box the result of my watching; the flies seemed to visit the flowers very seldom, it was a very bright hot afternoon tho’ with perhaps a little too much breeze, but after watching about 212 hours I only saw 4 or 3 flies of the kind I enclose visit.

after watching a group of 3 plants for some time I saw two or possibly three flies (one of which I send without the pollen masses) crawl into some flowers that were considerably open, that is so much open that the labellum was about in the position of the labellum in Fig B Page 94 of orchis Book.3 I observed that the flies in every* instance after crawling down to collect honey apparently from the stigma and beneath it instead of backing out, turned round and came out, and I saw that they could turn round just underneath the pollen masses or anther without touching them. These seemed to be essentially crawling flies, and I caught one which I send just to show which flies I then fancied could not be the agents.

These flies have not weight enough to depress the lip at all as I could plainly see; tho’ from trial I found the lips were depressed very easily, but the spring back seemed to me extremely slight, in one or two instances of flowers that certainly had never been visited, I found on pushing down gently the lip with a bit of grass that I had to give it a lift to get it into position again.

diagram In looking about for flowers with the labellum in the position of Fig A p. 94 I came upon one just in that position, namely the edges of the labellum near the hinge were just inside the body of the flower. the two frilled edges of the distal portion of the labellum were in contact; and on holding the flower opposite the eye and looking over the centre of the groove formed by the Junction of the two edges of the labellum one could just fairly see the yellow anther case but no lower    The moment I came on this flower I found a fly apparently of the same sort crawling out of the flower head formost without depressing the lip (i.e. not backing) with the pollen masses attached to his back (this is the fly I send you). If I had only had the luck to be a minute sooner I should have seen him enter.

I then went to some other flowers, and saw a small beetle or two crawl in with no effect also an ant, and a long bodied thin fly alighted but went off again— I saw no bee come near them within a yard or so. I saw another of same sort of fly on a flower (of the Epipactis) with what I am nearly sure sure was the remains of the pollen masses on his back in just the same position, but I was just too late with my bottle to catch him. on one flower I saw the pollen masses sticking to an upper petal, in another case to a lower sepal, in another to the top of an unopened bud.

I also found a longish hair or a leg sticking across a flower which drew out the pollen masses with it; I brought it away as carefully as possible, but it has vanished.

on going back to some flowers I had previously looked at, and in which there were no traces of pollen masses sticking to them or protruding; I found an ant in each of two flowers, one of which ants I send.   in one flower a single pollen mass was hanging down out of position, as if it has just been drawn out, and in the other the ant was sucking hard away and the pollen masses were behind him in the channel of the lip, and looked quite fresh.

I am almost certain that the ants did not back out but turned round. The flowers in which I found them were about in a state intermediate between A and B. I could easily go next Sunday and have another look, or get you some flowers, I might also have another look at the spring in hinge of labellum which then seemed so slight, but in some flowers I have brought away with me it seems a little greater.

You will find in box another much slighter fly which I caught in a flower not that he is worth sending.

I shall be down about the 13th or 14th.4

Your affect son | W. E Darwin

I took notes on the spot

I send Sat. Rev.5 please keep it as there is an Article I want to read when down with you as I have not read it

* I don’t remember seeing a fly back out

CD annotations

1.1 I went … 94 4.1] crossed pencil
4.8 could just … read it 14.2] crossed pencil
Top of letter: ‘WED | Epipactis palustris’ pencil


The year is established by the relationship between this letter and the letter to W. E. Darwin, 7 [July 1869].
Alum Bay and Colwell Bay are on the western side of the Isle of Wight. William refers to Epipactis palustris (marsh helleborine), a native British orchid commonly pollinated by bees, wasps, and syrphid flies.
William refers to Orchids.
CD was holidaying at Caerdeon, Barmouth, Wales (see ‘Journal’ (Correspondence vol. 17, Appendix II)).
Saturday Review.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

Orchids: On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing. By Charles Darwin. London: John Murray. 1862.


Observations on flies visiting Epipactis.

Letter details

Letter no.
William Erasmus Darwin
Charles Robert Darwin
Sent from
Source of text
DAR 162: 100
Physical description
ALS 12pp †

Please cite as

Darwin Correspondence Project, “Letter no. 6816,” accessed on 21 September 2023,

Also published in The Correspondence of Charles Darwin, vol. 17